Online financial planning service company LearnVest sells itself to Northwestern Mutual, confirming that IPOs are not the only successful exits.

Valuations are so rich and public markets so eager these days that most technology startups have tended to focus on initial public offerings as their primary exit strategy. But LearnVest, the online financial planning service, has another plan.

The six-year-old company announced on Wednesday that it's selling itself to Northwestern Mutual, a major insurance company based in Milwaukee. And while acquisitions may not seem as exciting as an IPO, they are certainly an important exit option.

"This is the culmination of so much blood, sweat, and tears, and words can't describe how proud and how invigorated I feel," says Alexa von Tobel, LearnVest's chief executive and chairman. LearnVest was an Inc. "30 under 30" company in 2010.

LearnVest was founded in 2009, a year after von Tobel dropped out of Harvard Business School to create the startup. At the time, she won a business plan competition run by Astia, a nonprofit for women entrepreneurs, and invested $75,000 of her own money to start the company.

Designed initially to offer dedicated financial-planning advice to women, it has morphed over time into a business that offers a combination of free and premium services to a broad spectrum of customers.

Although terms of the deal were not disclosed, von Tobel says it is expected to close in the second quarter of 2015. LearnVest will operate as an independent subsidiary of Northwestern Mutual, and von Tobel will continue her role as chairman and chief executive.

Northwestern Mutual, one of the largest insurance companies in the U.S., sells a wide variety of financial products, including life and disability insurance, annuities, and other investment products. It has 4.2 million customers, and creates financial plans for about 400,000 of them.

By contrast, LearnVest sells no products. It has 1.5 million customers that use its free personal financial management tool and content online, as well as 10,000 premium clients that pay a one-time set up fee of $300, plus $19 a month, to connect with LearnVest's team of certified financial planners for an individualized plan.

"What we will be doing over the next 24 months is integrating our technology to be able to deliver the plans in a better way," von Tobel says.

Since its founding, LearnVest has received $70 million in venture capital funding from 15 investors, including Accel Partners, American Express Ventures, and in its most recent Series D round, Northwestern Mutual. This last round of funding, $28 million in April, 2014, reportedly valued the company at $250 million.